Slack, the $2.8 billion business communications app, has long
advertised itself as a "freemium" product, where an unlimited
number of users can use it for free before deciding to upgrade
and pay money for more robust package with better features.

For example, on its
pricing page, it says, "Slack is free to use for as long as
you want, and with an unlimited number of people."

He says once he added 8,462 users to his Slack channel, it
stopped accepting new users.

"There's no mention of it anywhere, and yet it's clear this limit
exists. It's just hidden," Larson told Business Insider. "There
are hundreds of open source communities blindly signing up for
Slack, not knowing that they're rapidly hurdling toward this
limit that will basically halt their community's growth."

Now, this limit apparently strikes only when more than 8,462
users are added to a single channel. It's possible to create many
different channels within Slack, which is how most companies use
it.

But for an open source community like Free Code Camp, it's
important to use a messaging app that has the capacity to hold
thousands of users in a single chat room. Larson's site, for
example, has 35,000 total users, who mainly communicate through
one big general channel.

After discovering the user limit, Larson reached out to Slack's
service desk, but they also seemed confused with what they could
offer. As Larson
explains on his blog, Slack initially told him they could fix
it, only to retract later and tell him that he's reached the
"maximum user limit for a Slack team."

FreeCodeCamp

Because of the user limitation, and not having the resources to
upgrade to the paying service, FreeCodeCamp has decided to switch
back to Gitter, a Github based chatroom system, which offers
unlimited user space. Larson says the migration back to Gitter
will cost lots of resources because it will have move
infrastructure and all the current users who had signed up to its
Slack channel.

Larson says even if Slack
changes its policy, there's no chance he's going back to Slack.
"The cost of moving is tremendous," he said. "Slack is not a good
choice for large communities."

When Business Insider asked
about this limit, Slack's representative did not directly answer
the question, but directed us to its pricing
page, where it states, "We offer a free plan for
small teams, casual users, and anyone who wants to evaluate
Slack.

The spokesperson added:

Based on that, it’s
difficult to infer Slack would be an appropriate tool
for use by a 10,000 person
community. Slack
would love to be able to support all kinds of uses, but we
also need to
prioritize the uses for which Slack was designed and the
needs of existing
customers, who have very reasonable expectations
about ongoing
support and continued investment in the
product. It’s not
possible for one product to simultaneously serve the
specific needs of
working teams and large communities, at least not to
the level of
quality for which Slack aims. The requirements are just
too different and
often diametrically opposed.

Even so, Slack really should
update the language on its site. As seen in the screenshot below,
Slack does state there's "no limit on how many people you can add
to your team" on its free pricing page.